contract creation: use slug, calculate seed amounts from given probability

web/components/contracts-list.tsx

@@ -1,5 +1,7 @@
 import Link from 'next/link'
-import { Contract, deleteContract } from '../lib/firebase/contracts'
+import { useEffect, useState } from 'react'
+import { useUser } from '../hooks/use-user'
+import { Contract, deleteContract, listContracts } from '../lib/firebase/contracts'
 
 function ContractCard(props: { contract: Contract }) {
   const { contract } = props
@@ -49,8 +51,17 @@ function ContractCard(props: { contract: Contract }) {
   )
 }
 
-export function ContractsList(props: { contracts: Contract[] }) {
-  const { contracts } = props
+export function ContractsList(props: {}) {
+  const creator = useUser()
+
+  const [contracts, setContracts] = useState<Contract[]>([])
+
+  useEffect(() => {
+    if (creator?.id) {
+      listContracts(creator.id).then(setContracts)
+    }
+  }, [creator])
+
   return (
     <div className="bg-gray-200 shadow-xl overflow-hidden sm:rounded-md max-w-4xl w-full">
       <ul role="list" className="divide-y divide-gray-300">

web/lib/firebase/contracts.ts

@@ -10,6 +10,7 @@ import {
   getDocs,
   onSnapshot,
   orderBy,
+  getDoc,
 } from 'firebase/firestore'
 
 export type Contract = {
@@ -42,6 +43,15 @@ export async function setContract(contract: Contract) {
   await setDoc(docRef, contract)
 }
 
+export async function getContract(contractId: string) {
+  const docRef = doc(db, 'contracts', contractId)
+  const result = await getDoc(docRef)
+
+  return result.exists()
+    ? result.data() as Contract
+    : undefined
+}
+
 export async function deleteContract(contractId: string) {
   const docRef = doc(db, 'contracts', contractId)
   await deleteDoc(docRef)

web/lib/service/create-contract.ts

@@ -0,0 +1,51 @@
+import { Contract, getContract, setContract } from '../firebase/contracts'
+import { User } from '../firebase/users'
+import { randomString } from '../util/random-string'
+import { slugify } from '../util/slugify'
+
+// consider moving to cloud function for security
+export async function createContract(question: string, description: string, initialProb: number, creator: User) {
+    const slug = slugify(question).substr(0, 35)
+
+    const preexistingContract = await getContract(slug)
+
+    const contractId = preexistingContract
+        ? slug + '-' + randomString()
+        : slug
+
+    const { seedYes, seedNo } = calcSeedBets(initialProb)
+
+    const contract: Contract = {
+        id: contractId,
+        outcomeType: 'BINARY',
+
+        creatorId: creator.id,
+        creatorName: creator.name,
+
+        question: question.trim(),
+        description: description.trim(),
+
+        seedAmounts: { YES: seedYes, NO: seedNo },
+        pot: { YES: seedYes, NO: seedNo },
+
+        // TODO: Set create time to Firestore timestamp
+        createdTime: Date.now(),
+        lastUpdatedTime: Date.now(),
+    }
+
+    await setContract(contract)
+
+    return contract
+}
+
+export function calcSeedBets(initialProb: number, initialCapital = 1000) {
+    const p = initialProb / 100.0
+
+    const seedYes = p === 0.5
+        ? p * initialCapital
+        : -(initialCapital * (-p + Math.sqrt((-1 + p) * -p))) / (-1 + 2 * p)
+
+    const seedNo = initialCapital - seedYes
+
+    return { seedYes, seedNo }
+}

web/lib/util/random-string.ts

@@ -0,0 +1,2 @@
+
+export const randomString = () => Math.random().toString(16).substr(2, 14)

web/lib/util/slugify.ts

@@ -0,0 +1,11 @@
+
+export const slugify = (text: any, separator = '-'): string => {
+    return text
+        .toString()
+        .normalize('NFD')                   // split an accented letter in the base letter and the acent
+        .replace(/[\u0300-\u036f]/g, '')   // remove all previously split accents
+        .toLowerCase()
+        .trim()
+        .replace(/[^a-z0-9 ]/g, '')   // remove all chars not letters, numbers and spaces (to be replaced)
+        .replace(/\s+/g, separator)
+}

web/pages/contract/index.tsx

@@ -1,53 +1,31 @@
-import { useEffect, useState } from 'react'
+import router from 'next/router'
+import { useState } from 'react'
+
 import { ContractsList } from '../../components/contracts-list'
 import { Header } from '../../components/header'
 import { Spacer } from '../../components/layout/spacer'
 import { Title } from '../../components/title'
 import { useUser } from '../../hooks/use-user'
-import {
-  Contract,
-  listContracts,
-  setContract as pushContract,
-} from '../../lib/firebase/contracts'
+import { createContract } from '../../lib/service/create-contract'
+
 
 // Allow user to create a new contract
-// TODO: Extract to a reusable UI, for listing contracts too?
 export default function NewContract() {
   const creator = useUser()
-  const [contract, setContract] = useState<Contract>({
-    id: '',
-    creatorId: '',
-    question: '',
-    description: '',
-    seedAmounts: { YES: 100, NO: 100 },
-    pot: { YES: 100, NO: 100 },
 
-    // TODO: Set create time to Firestore timestamp
-    createdTime: Date.now(),
-    lastUpdatedTime: Date.now(),
-  } as Contract)
+  const [initialProb, setInitialProb] = useState(50)
+  const [question, setQuestion] = useState('')
+  const [description, setDescription] = useState('')
+  const [isSubmitting, setIsSubmitting] = useState(false)
 
-  const [contracts, setContracts] = useState<Contract[]>([])
-  useEffect(() => {
-    if (creator?.id) {
-      setContract((contract) => ({
-        ...contract,
-        creatorId: creator.id,
-        creatorName: creator.name,
-      }))
-      listContracts(creator.id).then(setContracts)
-    }
-  }, [creator])
+  async function submit() {
+    // TODO: add more rigorous error handling for question, description
+    if (!creator || !question || !description) return
 
-  async function saveContract() {
-    await pushContract(contract)
-    // Update local contract list
-    setContracts([{ ...contract }, ...contracts])
-  }
+    setIsSubmitting(true)
 
-  function saveField(field: keyof Contract) {
-    return (changeEvent: React.ChangeEvent<any>) =>
-      setContract((c) => ({ ...c, [field]: changeEvent.target.value }))
+    const contract = await createContract(question, description, initialProb, creator)
+    await router.push(`contract/${contract.id}`)
   }
 
   const descriptionPlaceholder = `e.g. This market will resolve to “Yes” if, by June 2, 2021, 11:59:59 PM ET, Paxlovid (also known under PF-07321332)...`
@@ -55,35 +33,25 @@ export default function NewContract() {
   return (
     <div>
       <Header />
+
       <div className="max-w-4xl py-12 lg:mx-auto px-4">
         <Title text="Create a new prediction market" />
+
         <div className="w-full bg-gray-200 rounded-lg shadow-xl p-6">
           {/* Create a Tailwind form that takes in all the fields needed for a new contract */}
           {/* When the form is submitted, create a new contract in the database */}
           <form>
-            <div className="form-control">
-              <label className="label">
-                <span className="label-text">Contract ID</span>
-              </label>
-              <input
-                type="text"
-                placeholder="e.g. COVID-123"
-                className="input"
-                value={contract.id}
-                onChange={saveField('id')}
-              />
-            </div>
-
             <div className="form-control">
               <label className="label">
                 <span className="label-text">Question</span>
               </label>
+
               <input
                 type="text"
                 placeholder="e.g. Will the FDA approve Paxlovid before Jun 2nd, 2022?"
                 className="input"
-                value={contract.question}
-                onChange={saveField('question')}
+                value={question}
+                onChange={e => setQuestion(e.target.value || '')}
               />
             </div>
 
@@ -91,79 +59,38 @@ export default function NewContract() {
               <label className="label">
                 <span className="label-text">Description</span>
               </label>
+
               <textarea
                 className="textarea h-24 textarea-bordered"
                 placeholder={descriptionPlaceholder}
-                value={contract.description}
-                onChange={saveField('description')}
+                value={description}
+                onChange={e => setDescription(e.target.value || '')}
               ></textarea>
             </div>
 
-            <div className="mt-6 grid grid-cols-1 gap-y-6 gap-x-4 sm:grid-cols-6">
-              <div className="sm:col-span-3">
             <div className="form-control">
               <label className="label">
-                    <span className="label-text">Yes Seed</span>
+                <span className="label-text">Initial probability: {initialProb}%</span>
               </label>
+
               <input
-                    type="number"
-                    placeholder="100"
-                    className="input"
-                    value={contract.seedAmounts.YES}
-                    onChange={(e) => {
-                      setContract({
-                        ...contract,
-                        seedAmounts: {
-                          ...contract.seedAmounts,
-                          YES: parseInt(e.target.value),
-                        },
-                        pot: {
-                          ...contract.pot,
-                          YES: parseInt(e.target.value),
-                        },
-                      })
-                    }}
+                type="range"
+                className="range-primary"
+                min="1"
+                max={99}
+                value={initialProb}
+                onChange={e => setInitialProb(parseInt(e.target.value))}
               />
             </div>
-              </div>
-
-              <div className="sm:col-span-3">
-                <div className="form-control">
-                  <label className="label">
-                    <span className="label-text">No Seed</span>
-                  </label>
-                  <input
-                    type="number"
-                    placeholder="100"
-                    className="input"
-                    value={contract.seedAmounts.NO}
-                    onChange={(e) => {
-                      setContract({
-                        ...contract,
-                        seedAmounts: {
-                          ...contract.seedAmounts,
-                          NO: parseInt(e.target.value),
-                        },
-                        pot: {
-                          ...contract.pot,
-                          NO: parseInt(e.target.value),
-                        },
-                      })
-                    }}
-                  />
-                </div>
-              </div>
-            </div>
-
-            {/* TODO: Show a preview of the created market here? */}
 
             <div className="flex justify-end mt-6">
               <button
                 type="submit"
                 className="btn btn-primary"
+                disabled={isSubmitting}
                 onClick={(e) => {
                   e.preventDefault()
-                  saveContract()
+                  submit()
                 }}
               >
                 Create market
@@ -175,7 +102,8 @@ export default function NewContract() {
         <Spacer h={10} />
 
         <Title text="Your markets" />
-        <ContractsList contracts={contracts} />
+
+        <ContractsList />
       </div>
     </div>
   )